Preparation Of Phenol Formaldehyde Resin-based Carbon Molecular Sieves For Air Separation By PSA

Carbon Molecular Sieves (CMS), which have the mechanism of molecular sieving, is a kind of carbonaceous adsorbent with a sharp distribution in micropore range. Similar to the chemical construction of activated carbon, CMS possesses well-developed pore structure and special surface properties. Due to its unique pore structure and selective adsorption of gases of different sized-molecules, CMS is widely used in gas separation field. Since those qualified CMS should not only high in adsorptive selectivity but also in adsorption capacity, uniformed and appropriate-sized apertures and relatively large pore volumes are further required. Although domestic researches have made some achievements, there are still problems such as low technology process repeatability, poor product performance and deficiencies in the grasp and control of internal mechanisms of critical process step during the preparation process.Taking thermosetting phenolic resin as the raw material, this paper explored the qualitative changes and effects of technological parameter to char in phenolic resin pyrolysis.Instinctive reactions of different products were deduced according to the results drawn from the phase transitions between solid, liquid and gas with the influence of temperature.The changes of grindabilities and pore structures of carbonized materials in various pyrolysis temperatures were inspected and its relations with internal reactions were also covered.Finally, the paper studied and found that the pyrolysis heating rate and granularity of raw materials showed great effect on the varied pore structure of carbonized products.Taking phenolic resin char as raw material and thermosetting phenolic resin as binder, the methods to make CMS was attempted. During the process, the effect of key processing steps such as usage of binders, carbonization and activation on CMS intermediates and relevant problems like internal mechanisms of each steps and the controlling issue are explored.Based on changes of pore structure, adsorption and separation performances of intermediates in the pressure-swing adsorption process, the best proportions of the binder, parameters of carbonization and activation were determined. That is, with a 10℃/min heating rate of,775℃ temperature,40minutes reaction time of carbonization,120 minutes activation time and an activator content of 80% or 120%, a intermediate of proper pore structure will be produced to serve as the raw material of deposited carbon to make CMS.On the basis of the above experiments, the paper also tried to find out the mechanism of carbon deposition processes. During the tests, two-step approach was adopted to adjust pore structures. In the first stage, benzene deposition was employed to adjust the pore structures of CMS on the condition of 770℃ deposition temperature,20% benzene content and 110 minutes deposition time. As a result, a deposition sample which could concentrate the N2 above to 97% in the PSA was produced. In the next step, the deposition methods of low concentration and reactivation were tested. With a deposition temperature of 770℃, benzene content 10% and 40 minutes deposition time, a CMS sample with 99% N2 in the PSA was produced by low concentration benzene deposition. When it comes to the method of reactivation, a CMS sample with 99.0% N2 in the PSA was produced with 800℃ activation temperature,10% concentration of activator and 20 minutes of activation time.